Idk how tall you are but, I like to put my middle finger around the rings.
When I started doing these it helped me a lot
1. Squezze the bar really tight and act as if you're trying to pull it apart
2. When bringing the bar down really focus on using your lats
Bench Press Articles About Bench Press Technique
there are a sh*tload of articles in here that helped me.
this is pretty basic stuff but a lot overlook it
http://www.criticalbench.com/bench-press-tip.htm